1. Field of the Invention
The present invention relates to a semiconductor laser element, a semiconductor laser device, and an optical apparatus employing the same, and more particularly, it relates to a semiconductor laser element formed with a facet coating film on a cavity facet, a semiconductor laser device, and an optical apparatus employing the same.
2. Description of the Background Art
A semiconductor laser element formed with a facet coating film on a cavity facet is known in general, as disclosed in each of Japanese Patent Laying-Open Nos. 2000-349389 and 2006-186228, for example.
Each of Japanese Patent Laying-Open Nos. 2000-349389 and 2006-186228 discloses a semiconductor laser element formed with a facet coating film on a cavity facet on a laser beam-emitting side. In this facet coating film, an optical thin film layer of Al2O3 and a photocatalytic layer of TiO2 are stacked successively from the side closer to the cavity facet. Due to the optical thin film layer, the laser reflectance of the cavity facet is set to a prescribed magnitude, and due to the photocatalytic layer, contaminants (organic substances) adhering to the outermost surface of the facet coating film are decomposed.
In the semiconductor laser element disclosed in each of Japanese Patent Laying-Open Nos. 2000-349389 and 2006-186228, the photocatalytic layer is provided on the outermost surface of the facet coating film, and hence the contaminants adhering to the outermost surface of the facet coating film are conceivably removed to some extent due to photocatalytic action. However, in a blue-violet semiconductor laser element having a short lasing wavelength of about 405 nm or the like, adherence of contaminants to an emitting facet tends to be significantly promoted due to an increase in light energy (light density). Therefore, in the semiconductor laser element including the facet coating film made of only the optical thin film layer controlling the reflectance and the photocatalytic layer, the amount of deposition of contaminants may exceed the amount of removal of contaminants, and adherence of contaminants to the outermost surface of an emitting facet cannot be reliably inhibited.